Hi,

Would be nice if ES can send an invite to other user via Facebook/Twitter/Linked, etc...

Maybe add an option for new user to invite their Facebook/Twitter/Linked friend's after registration.
A built-in feature to send an invite from within ES user to Facebook/Twitter/Linked users.
It can be optional or required depends on the setting from backend.

For site owner, I think this would be a great tool to keep new members growing.